1. Field of the Invention
The present invention relates to a zoom lens suitable for use in a compact digital camera and to an image pickup apparatus equipped with the same.
2. Description of the Related Art
In recent years, various categories of digital cameras (or electronic cameras) ranging from portable popular-priced cameras to professional-use high-function cameras have been developed. In the category of portable popular-priced cameras, among them, there has arisen a demand for technologies that realize inexpensive video cameras and digital cameras that are small in depth, have good usability, and have a high zoom ratio covering a wide focal length range from the wide angle end to the telephoto end while achieving good image quality.
The most serious bottleneck in sliming a camera with respect to the depth direction is the optical system, in particular the thickness of the zoom lens system, that is, the distance from the lens surface closest to the object side to the image plane. The main trend in the field of technologies for slimming the camera body is to use what is called a collapsible lens barrel in which the optical system extends from the camera body when in use and collapses to be housed in the camera body when not in use. However, in the case where a collapsible lens barrel is used, it takes a significant time to extend the lens barrel from its housed state to the state ready for use. This is not desirable from the viewpoint of usability. In addition, having a movable front most lens unit (i.e. the lens unit closest to the object side) is undesirable from the viewpoint of water/dust resistance.
In recent years, there have been developed optical systems having an optical path (or optical axis) that is bent by a reflecting optical member such as a mirror or a prism to achieve a camera that is advantageous from the viewpoint of water/dust resistance and very small in depth, and can be ready for use in a camera without taking start-up time (to extend the lens) that is required in the case of the collapsible lens barrel. In such optical systems, the lens unit closest to the object side is a fixed lens unit that does not change its position, and the aforementioned reflecting optical member is provided in this lens unit, whereby the optical path after the reflecting optical member is deflected to extend in a horizontal or vertical direction of the camera body to make the depth as small as possible.
On the other hand, in video cameras and digital cameras categorized in the portable type, although the optical system generally has an angle of view of about 30 degrees at the wide angle end, optical systems having a wider angle of view are desired to extend the shooting situations. Examples of the zoom lens using a bent optical system include those described in Japanese Patent Application No. 2004-354871 and No. 2004-354869.